- Co2(CO)6-propargyl cation mediates glycosylation reaction by using thioglycoside
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We discovered that the cobalt-propargyl cation can mediate the glycosylation reaction by activating the thioglycoside donor. The glyco-oxacarbenium cation was formed by transferring the thio-aglycone to the cobalt-propargyl cation that was generated from the cobalt-propargylated acceptor in situ via the activating with Lewis acid. The reactivity of the donor (Armed or dis-armed) and the amount of the Lewis acid control the releasing rate of the cobalt-propargyl group.
- Xia, Meng-jie,Yao, Wang,Meng, Xiang-bao,Lou, Qing-hua,Li, Zhong-jun
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supporting information
p. 2389 - 2392
(2017/05/29)
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- Nucleofuge Generating Glycosidations by the Remote Activation of Hydroxybenzotriazolyl Glycosides
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Hydroxybenzotriazole is routinely used in peptide chemistry for reducing racemization due to the increased reactivity. In this article, very stable hydroxybenzotriazolyl glucosides were identified to undergo glycosidation. The reaction was hypothesized to go through the remote activation by the Tf2O at the N3-site of HOBt followed by the extrusion of the oxocarbenium ion that was attacked by the glycosyl acceptor. Further, equilibration of the zwitterionic benzotriazolyl species makes the leaving group noncompetitive and generates the nucleofuge that has been reconverted to the glycosyl donor. The reaction is mild, high yielding, fast and suitable for donors containing both C2-ethers and C2-esters as well. The regenerative-donor glycosidation strategy is promising as it enables us to regenerate the glycosyl donor for further utilization. The utility of the methodology for the oligosaccharide synthesis was demonstrated by the successful synthesis of the branched pentamannan core of the HIV1-gp120 complex.
- Neralkar, Mahesh,Mishra, Bijoyananda,Hotha, Srinivas
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p. 11494 - 11504
(2017/11/10)
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- Four Different Regioisomeric Polycarbonates Derived from One Natural Product, d -Glucose
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Strategies for the preparation of polycarbonates, derived from the natural product d-glucose, which have the potential to degrade back into their bioresorbable starting material and CO2, were developed. By employing established carbohydrate pro
- Lonnecker, Alexander T.,Lim, Young H.,Felder, Simcha E.,Besset, Céline J.,Wooley, Karen L.
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p. 7857 - 7867
(2016/11/09)
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- Gold-catalysed glycosylation reaction using an easily accessible leaving group
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Gold(iii)-catalysed glycosylation reaction has been developed by employing a new and easily accessible leaving group synthesized from ethyl cyanoacetate. Several nucleophiles like alcohols, thiols, allyltrimethylsilane, trimethylsilyl azide and triethylsilane have been reacted to make the corresponding glycosides in good yields and with marginal to excellent α-selectivity. This journal is
- Koppolu, Srinivasa Rao,Niddana, Ramana,Balamurugan, Rengarajan
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supporting information
p. 5094 - 5097
(2015/05/13)
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- β-Rhamnosides from 6-thio mannosides
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Upon condensation of 6-thio-6-deoxy-mannosyl donors 1,2-cis products are obtained with a high degree of stereoselectivity. Subsequent reductive removal of the 6-thio functionality gives 1,2-cis rhamnosides. The 1,2-cis-selectivity can be rationalized with
- Christina, Alphert E.,Es, Daan Van Der,Dinkelaar, Jasper,Overkleeft, Hermen S.,Marel, Gijsbert A. Van Der,Codee, Jeroen D. C.
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p. 2686 - 2688
(2012/04/10)
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- Some observations on the reductive ring opening of 4,6-O-benzylidene acetals of hexopyranosides with the borane trimethylamine-aluminium chloride reagent
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Reductive ring openings of 3-O-benzoyl-4,6-O-benzylidene-d-glucopyranosides with BH3·NMe3-AlCl3 are accompanied by side reactions, such as debenzoylation and reduction of the benzoate to benzyl ether. This phenomenon was r
- Daragics, Katalin,Szabó, Pál,Fügedi, Péter
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experimental part
p. 1633 - 1637
(2011/09/14)
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- Rapid assembly of gp120 oligosaccharide moieties via one-pot glycosidation-deprotection sequences
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Mannosyl trihaloacetimidate donors equipped with a 2-O-Fmoc group can be effectively activated by catalytic Bi(OTf)3 in glycosidations. Despite the expected participating effect of the Fmoc group, the reaction solvent was found to be decisive f
- Pastore, Antonello,Adinolfi, Matteo,Iadonisi, Alfonso,Valerio, Silvia
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experimental part
p. 1316 - 1323
(2010/10/02)
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- One-pot catalytic glycosidation/Fmoc removal - An iterable sequence for straightforward assembly of oligosaccharides related to HIV gp120
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The removal of a transient Fmoc protecting group can be simply performed by the addition of excess Et3N just after the accomplishment of a Bi(OTf)3-promoted glycosidation reaction. The obtained oligosaccharide can be directly employed as a glycosyl acceptor for further elongation of the saccharide. The preparation of biologically important, linear and branched mannans incorporated into HIV gp 120 demonstrates that the iteration of this one-pot sequence leads to a very straightforward oligosaccharide assembly.
- Pastore, Antonello,Adinolfi, Matteo,Iadonisi, Alfonso,Valerio, Silvia
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experimental part
p. 711 - 718
(2010/03/24)
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- Regio- and chemoselective reductive cleavage of 4,6-O-benzylidene-type acetals of hexopyranosides using BH3·THF-TMSOTf
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Benzylidene-type cyclic acetals of carbohydrates undergo efficient reductive ring opening using BH3·THF and a catalytic amount of TMSOTf at room temperature. 4,6-O-Benzylidene-hexopyranosides afford the corresponding 4-O-benzyl ethers exclusive
- Daragics, Katalin,Fügedi, Péter
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experimental part
p. 2914 - 2916
(2009/09/06)
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- Efficient synthesis of man2, man3, and man 5 oligosaccharides, using mannosyl iodide donors
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A highly efficient protocol for making Man3 and Man5 oligosaccharides with use of orthogonally protected glycosyl iodide donors has been developed. Glycosylation of a C-2-O-acetyl mannosyl iodide donor in the presence of silver trifl
- Lam, Son N.,Gervay-Hague, Jacquelyn
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p. 8772 - 8779
(2007/10/03)
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- Ditritylation of Methyl and Benzyl α-D-Gluco-, -Manno-, and -Galactopyranosides and Preparation of Their Partially Benzylated Derivatives
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The ditritylation of methyl and benzyl α-D-gluco-, -manno-, and -galactopyranosides with trityl chloride in pyridine at 70 deg C proceeds in a regioselective manner to give the 2,6-ditrityl ethers of the glucosides, the 3,6-ones of the mannosides, and bot
- Koto, Shinkiti,Morishima, Naohiko,Yoshida, Toyosaku,Uchino, Masaharu,Zen, Shonosuke
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p. 1171 - 1175
(2007/10/02)
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- SYNTHESIS OF A BRANCHED D-GLUCOTETRAOSE, THE REPEATING UNIT OF THE EXTRACELLULAR POLYSACCHARIDES OF Grifola umbellate, Sclerotinia libertiana, Porodisculus pendulus, AND Schizophyllum commune FRIES
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The synthesis of D-glucotetraose, 3-O--6-O-β-D-glucopyranosyl-α (and β)-D-glucopyranose, the repeating unit of the extracellular polysaccharides of Grifora umbellata, Sclerotinia libertiana, Porodisculus pendulus, and Schizophyllum commune Fries, is described.
- Ogawa, Tomoya,Kaburagi, Toshiaki
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- ONE-STAGE GLYCOSYLATION USING PROTECTED GLYCOSE: THE SYNTHESIS OF O-β-D-GLUCOPYRANOSYL-(1->3)-O-6)>-D-GLUCOPYRANOSE
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The one-stage β-glycosilation of benzyl 3-O-acetyl-2,4-di-O-benzyl-α-D-glucopyranoside ( 1 ) with 2,3,4,6-tetra-O-benzyl-α-D-glucopyranose ( 2 ) using a mixture of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine, followed by deacetylation, gave benzyl O-(2,3,4,6-tetra-O-benzyl-β-D-glucopyranosyl)-(1->6)-2,4-di-O-benzyl-α-D-glucopyranoside ( 3 ).The disaccharide derivative 3 was then subjected to the β-glucosylation, followed by catalytic hydrogenation, to afford O-β-D-glucopyranosyl-(1->3)-O-6)>-D-glucopyranose ( 4 ).The key intermediate 1 was prepared from D-glucose by way of a Fischer reaction, triphenylmethylation, a controlled benzylation, and detriphenylmethylation.
- Koto, Shinkiti,Inada, Shigeru,Yoshida, Toyosaku,Toyama, Miyako,Zen, Shonosuke
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p. 255 - 259
(2007/10/02)
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- SYNTHETIC STUDIES ON CELL SURFACE GLYCANS 3 BRANCHING PENTASACCHARIDES OF GLYCOPROTEIN
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Synthetic routes for the branching pentasaccharides 4 and 5 of glycoproteins are described in a regio- and stereo-controlled way.
- Ogawa, Tomoya,Katano, Kiyoaki,Sasajima, Kikuo,Matsui, Masanao
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p. 2779 - 2786
(2007/10/02)
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